Have been cheated and stayed in the relationship

Ok ladies, im new here and I was wondering if I could get some new and different perspective of what had happened to me 4 years ago. My husband of then 7.5 years cheated on me with my so called friend, who just so happens to be his friends ex wife. I was devastated, but I decided to stay in the marriage. To try to work it out and figure out exactly what had happened. We all know that marriage is a two street, and that because something has gone wrong, is not always just th fault of one person. We now have a beautiful baby girl. BUT, I'm just not happy. And evetytime we get and argument, my mind is always telling me to file for a divorce. So what do you think??? Am I really doing the right thing to stay around?? Or am I just dragging the enevitable?!!